Lens



Aug. 18, 1925.

H. K. PARSONS LENS Filed Feb. 1, 1921 w w m INVENTOR HAROLD K- PfiRSONS ATTORNEYS Patented Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

HAROLD K. PARSONS, OE'SOUTHBRIDGE, MASSACHUSETTS, ASSIGIIOR TO AMERICAN OPTICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY AS0CIA- 'rIoN' or MASSACHUSETTS.

LENS.

Application filed February 1, 1921. Serial No. 441,585.

To all whom it may concern:

Be it known that I, HAROLD K. PARsoNs, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Lenses, of which the following is a specification.

This invention relates to improvements in lenses and has particular reference to an improved form of lens as produced by the process described in the Patent 1,370,042.

One of the principal objects of the present invention is the provision of an improved form of bifocal lens which shall have a wider reading field than previously known forms of two part bifocals.

'A further object of the present invention is the provision of a lens of this character which while attaining a wide reading field, shall have the segment properly centered in the vertical meridian, that-is to say, shall be constructed with the optical center of the countersink substantially at the geometrical center of the countersink in the vertical meridian and shall thus minimize difficulties liable to be present through prismatic displacement, or the like.

A further object of the invention is the provision of a lens having a wide reading field coupled with a thin supplemental portion or segment.

Other objects and advantages of the improved construction should be readily apparent by reference to the following specification taken in connection with the accompanying drawingsfand' it will be understood that any modifications in the specific details of construction shown and described may be made within the scope of the appended L claims without departing from or exceeding the spirit of the invention.

Figure I is a plan view illustrating a step in the process of formation of the improve ens.

Figure II is a sectional view through a pair of blanks of the improved lenses.

Figure III is a sectional view through one of said blanks.

Figure IV is. a sectional view through a semi-finished lens.

Figure V is a plan view thereof.

Figure VI is a plan view illustrating a different manner of constructing thelens to secure three instead of two lenses with the same operation.

Figure ,VI-I is a vertical sectional view through the lens embodying the improvements.

. In the drawings, the numeral 1 designates the major portion of an opththalmic lens blank having formed therein a countersink 2 to receive the segment 3, the segment being of a different index of refraction from the major portion, and the bifocal or multifocal addition in the lens being secured through the interengagement of the countersink and segment with the curves on the two sides of the segment so related as on account of the difference in refraction of the two glasses to produce the desired additive power or powers. It. will be understood that it is ordinarily customary in a lens of this type to form on one face, as at 4, a single continuous curve extending over both the main lens and the segment, the power difference, therefore, being accomplished by the formation of a countersink in the major portion into which a curved face on the segment fits.

Prior to this invention, however, it has been the practice to form a circular countersink near one edge of the lens and to mount the segment in this circular countersink securing it in place by fusion. This means that the final field of the lens will be circular and will have but limited lateral extension while requiring that the blanks be made up' or shaped to produce a common circular'recess having its central portion ineach blank lower than the terminal or edge portions as respects the blank, so that in the vertical meridianv the optical center of the curve formed'will be about in the geometrical center or intermediate the edge and point of merger of the countersink curve andtop surface of'the bifocal, as will be understood by,

reference to Figure IL The part-S thus nal center portion of the segment 3, reducing it to the form of a concavo convex lens, as indicated in connection with Figure IV. On

the opposite face of the lens the surface 5 is' preferably reducing the lens formed to the desired thickness and to the finally finished form shown in connection with Figure VII. It will then be seen by reference to Figures V and VII that the lens has a substantially semi-circular segmental portion as viewed from the front, coupled with a segmental portion having the optical center of its countersink curve substantially at the geometrical center in the vertical meridian of the reading portion, thus allowin the eye in looking downward, as in rea ing, to 'look through said central portion and at a substantial angle to the parts as indicated by the line 6-7 in connection with Figure VII of the drawings, obtaining the best optical results possible with this form of lens and at the same time facilitating its manufacture.

and greatly increasing the possible speed of production as well as providing a. more satisfactory lens.

I claim:

1. A blank for a pair of multifocal lenses comprising a pair of major portions disposed in tilted relation one to the other, a single countersink formed in the'major portions, and a segment mounted in the countersinks and uniting the major portions, substantially as illustrated.

2. As an article of manufacture, a blank for multifocal lenses, comprising major portions relatively tilted one to the other, a countersink formed in said major portions, anclli a single segment secured in said counters1n 3. A multifocal lens blank, comprising a plurality of major lens portions, and pro vided with an arcuate countersink formed centrally therein, a segment secured in said countersink, said major lens portions being tilted relatively to the coinciding centers of the countersink and segment, whereby a plurality of lenses, each with a reading and a distance portion, may be cut from the blank, each reading portion being originally a part of said segment. I

In testimony whereof I have ailixed my signature, in presence of two witnesses.

, HAROLD K. PARSONS. Witnesses:

ALICE G. HASKELL,

SUSAN CASAZZA. 

